This invention relates to a paper surface cleaning device for removing fine paper dusts, etc., from the surface of a printing paper.
A band-like printing paper is cleaned by a cleaning device before it is supplied to a printing portion of a printing machine. Such a cleaning device is disclosed in Japanese Laid-Open Publication HEI5(1993)-193112. The cleaning device has a diaphragm to be expanded and a compressed air source for expanding the diaphragm. The diaphragm is disposed opposite to a running path of the printing paper. Over and under the diaphragm are disposed a feeding roller and a take-up roller which make a running path of a cleaning cloth. The diaphragm pushes a portion of cleaning cloth to the printing paper running along its running path. Water is supplied by a water nozzle onto the cleaning cloth. The nozzle can supply water onto the cleaning cloth through its total width. The cleaning cloth gets wet with the water injected through the water nozzle, and the diaphragm is expanded to push the wet cleaning cloth to the printing paper thereby to wipe or clean the surface of the printing paper.
However, in the conventional paper surface cleaning device, since water is supplied to the cleaning cloth through the water nozzle, the wet state of the cleaning cloth is apt to be uneven in its widthwise direction, and the paper dusts cannot be removed uniformly from the printing paper in its widthwise direction. Furthermore, the wet state of the printing paper is uneven in its widthwise direction. It is necessary to change the amount of water to be supplied in accordance with the change of the running speed of the printing paper. However, in the conventional cleaning device having a nozzle as a damping device for dampening the cleaning cloth, such a control is remarkably difficult to decrease the quality in printing.
Thereupon, the inventor tried to make various experiments. For example, instead of the water nozzle for supplying water to the cleaning cloth, a brush was used. However, also in this case, an even water supply to the cleaning cloth could not be obtained. In general, in printing, dampening water is supplied by a dampening device to the outer circumferential surface of a cylinder together with ink. The dampening device comprises a water fountain roller dipped into the water in a water pan, a forme dampening roller, etc.. The inventor thought that the dampening device might be adapted for a water supply device to the surface of the cleaning cloth. In the conventional dampening device, damping water is finally supplied to a relatively stiff body such as a printing plate wound around the cylinder. In contrast, in the dampening water supply device for supplying damping water to the cleaning cloth, the cleaning cloth is not stiff body. Therefore, in a conventional dampening arrangement and a paper surface cleaning device, the objects to which the damping water supplied are different from each other. In these conditions, the inventor paid attention to the fact that a roller could push effectively the cleaning cloth onto the printing paper and could be rotated at a predetermined speed.